1. Field of the Invention
This invention relates generally to thrust reversers for jet engines, and more particularly to a target type thrust reverser in which the doors are mounted to sliding pivot joints.
2. Description of the Related Art
In the field of jet engines, and particularly in the field of jet aircraft engines, it frequently becomes advantageous to reverse the thrust of the engine in order to supply a braking force to the structure to which the engine is attached. On jet aircraft, thrust reversers are typically used to shorten the distance that the aircraft travels on the runway after landing and to enhance safety when braking the aircraft on a damp or icy runway. Various types of thrust reversers have been developed for such purposes.
In general, thrust reversers fall into one of two categories: (1) fan only reversers, which reverse only the fan bypass stream but not the core engine exhaust, and (2) full jet reversers, which reverse most of the core engine exhaust as well as the fan bypass stream. Thrust reversers in the latter category are sometimes referred to as “target” type reversers because they involve thrust reverser doors that are deployed into the engine exhaust stream aft of the exit plane to form a target onto which substantially the entire engine exhaust stream impinges.
An example of a fan only reverser is shown in U.S. Pat. No. 5,197,693, issued to Remlaoui on Mar. 30, 1993 (“Remlaoui”). The Remlaoui reverser comprises a plurality of blocker doors that are mounted on sliding hinges about the periphery of the engine nacelle and that are actuated by extensible rods. In their stowed positions, the blocker doors form a streamlined part of the annular duct through which fan air passes outside the engine core. As the extensible rods are actuated, the blocker doors are rotated into the duct to divert the fan airstream out of the nacelle in a forward direction. Because fan only reversers are capable of reversing only the fan air and not the core engine exhaust, fan only reversers are not capable of providing as much reverse thrust as a full jet thrust reverser.
One of the most common types of target thrust reversers is a four-bar link system such as that disclosed in U.S. Pat. No. 4,005,836, issued to Mutch on Feb. 1, 1977 (“Mutch”). In a four-bar link system, each one of a pair of doors is mounted to the engine with four bars—two bars (one forward and one aft) on each side of the door. Each bar has one end pinned to the engine structure and the other end pinned to the door. The pin connections at the respective ends of the forward bars are on a common axis that runs transverse to the engine axis, and likewise the pin connections at the respective ends of the aft bars are on a common axis that runs transverse to the engine axis. Because the forward bars are longer than the aft bars, the four bars cooperate to allow the door to both rotate and translate as the bars are pivoted about the points that are pinned to the engine structure. The doors are thus capable of movement between a stowed position, in which the doors lie adjacent the engine nozzle out of the exhaust stream, and a deployed position, in which the doors are disposed within the exhaust stream aft of the engine exit. Although a four-bar link system such as that disclosed in Mutch reverses substantially all of the engine exhaust and therefore provides considerably more reverse thrust than a fan only thrust reverser, a four-bar link system has the drawback of increased weight because the structure must be quite heavy in order to carry the increased forces and moments that the system generates. The forces are greater because the doors divert a much greater volume of air, and the moments are greater because the bars place the doors at a significant distance away from the pivot joints. Additionally, the four bars constitute extra moving parts that add an extra level of complication and cost.
Thus, it would be a significant advancement in the art to provide a jet engine thrust reverser that has a large thrust reversal capacity, reduced weight, simple operation, improved reliability, and reduced cost.